Research suggests that 90% of all commercial shampoos and personal care products, (including toothpastes), use a detergent called sodium dodecylsulfate (SDS), also know as sodium laurel sulphate (SLS), sodium lauryl sulphate or sodium laureth sulphate (SLES).
These detergents are the foaming agent in personal care products. They are used because they are cheap - a small amount generates a large amount of foam.
Sodium lauryl sulphate is considered to be the most harmful - it is used in testing laboratories as the standard ingredient (upon which all other substances are compared) for irritating the skin. Industrial uses of SLS include garage floor cleaners, engine de-greasers and car wash soaps.
Studies show its danger to be considerable when used in personal care products. A solution of just 2% SLS can increase skin thickness, cause irritation, inflammation, and increase other forms of immune activity in the skin. Some shampoos contain more than 50% SLS!
Other research suggests that SLS and SLES may cause potentially carcinogenic nitrates and dioxins to form in shampoos and cleansers by reacting with other commonly used ingredients, such as MEA, TEA and DEA. Nitrates - which are easily absorbed by the body - may enter the blood stream from just one shampooing.
Younger people, particularly children are most susceptible to the effects of SLS and LES.
Sodium laureth sulphate (SLES), - the alcohol form of SLS - is slightly less irritating, but can be more drying to the skin. Both SLES and SLS have been found to damage hair follicles and cause hair loss.